July 6 (UPI) -- A former naval diver died Friday while placing air tanks in the Thailand cave where 12 boys and their soccer coach are trapped -- the first death in the weeks-long ordeal.
Saman Kunan, a former Thailand Navy SEAL, died from asphyxiation while attempting to return to a command center located a mile inside the cave, government officials said.
Kunan, 38, had been delivering oxygen tanks to the trapped boys.
"I can't believe this happened," Sgt. Anuram Kaewchano, a friend of Kunan's, told CNN. "He was very fit, he exercised every day, and he was a triathlete. Our last trip together was to Malaysia."
Navy SEAL Rear Adm. Aphakorn Yookongkaew said Kunan may have passed out and drowned.
"Definitely you can feel it that it has an effect, but we're moving on. Everyone is a professional so we're trying to put it away and avoid it happening again," volunteer diver Mikko Paasi said. "Everybody is focusing on getting these boys out -- keeping them alive or getting them out."
Rescuers are still trying to free the boys and their soccer coach, who entered the cave two weeks ago. They were missing until Monday, when divers found them deep in one of the cave's chambers.
Heavy rains expected Sunday could seriously complicate the rescue mission, as workers have been racing to drain the water level to a point they can extract the team. Otherwise, the boys will have to scuba dive a long distance to get out. Some of them can't swim.
Thursday, FIFA president Gianni Infantino invited the team and their coach to the World Cup final in Moscow on July 15 if they are freed by then.
"We have been anxiously following news of the rescue operation," the global soccer body said.
"If, as we all hope, they are reunited with their families in the coming days, and their health allows them to travel, FIFA would be delighted to invite them to attend the 2018 World Cup final in Moscow as our guests."